Note: Descriptions are shown in the official language in which they were submitted.
CA 02696171 2010-02-10
A Method for Mapping a Physical Downlink Control Format Indicator Channel to
Physical Resources
TECHNICAL FIELD
The present invention relates to the field of broadband wireless communication
systems, especially to a method for mapping a physical downlink control format
indicator channel to physical resources in a 3GPP Long Term Evolution
(shortened as
LTE) system.
1o BACKGROUND
In an LTE system, since resources exist in two dimensions, i.e. time and
frequency. Accordingly, the allocation of the resources and their
representation
method become quite complicated, especially when a bandwidth is relatively
wide,
consideration must be given to such requirements as not only the flexibility
of the
resources allocation but also the size of the related bandwidth, etc.
Fig. 1 is a schematic illustration of a resource block and a resource element
in a
3GPP LTE (with 5M-bandwidth) system. It is specified in the LTE system that
the
length of a sub-frame in time is 1 ms, and one sub-frame is comprised of two
equal
time slots (Time Slot 1 and Time Slot 2), the length of time of each time slot
is 0.5ms.
One resource element contains one Orthogonal Frequency Division Multiplexing
(shortened as OFDM) symbol, and one subcarrier in each OFDM symbol belongs to
the resource element. While the usual method of resource representation is
defining
a basic Resource Block (shortened as RB), and then carrying out the resources
allocation in the unit of RB.
In the LTE system, a downlink mainly includes multiple downlink channels such
as a Physical Control Format Indicator Channel (shortened as PCFICH), etc. A
representation method for mapping a physical downlink control format indicator
channel to physical resources is given in a current draft standard, which is
specifically
described as below:
mapping y(0),...y(3) to the resource elements in which a resource element
group
CA 02696171 2010-02-10
k locates, and k= ko ;
mapping y(4).... y(7) to the resource elements in which a resource element
group
k locates, and k= ko + LNRB /4 J,
mapping y(8),...y(11) to the resource elements in which a resource element
group k locates, and k= ko +L2NR8 /4];
mapping y(12).... y(15) to the resource elements in which a resource element
group k locates, and k= ko +L3NRB/4 J;
wherein, ko = N;p"mod(NRB /2) , and it is necessary to carry out a moduius of
NRBNRB on k;
to wherein, y(0),...,y(15) stand for the data in the physical downlink control
format
indicator channel after code modulation, and the NRB stands for the quantity
of
resource blocks in the system bandwidth, and the Np" is the proprietary ID
(identity)
of each cell.
Taking the 3GPP LTE (with 5M-bandwidth) system for example, as shown in Fig.
1s 1, a 5M-bandwidth downlink in the LTE contains a total of 512 subcarriers,
the 300 of
which in the middle are usable subcarriers; each resource block contains
continuous
12 subcarriers, therefore the 5M bandwidth contains a total of 25 resource
blocks.
One resource block contains 4 pilot elements, and except the pilots, every
four
remaining resources elements are combined into a resource element group, so
there
2o are a total of 50 resource element groups.
The physical downlink control format indicator channel is mapped to the first
OFDM symbol in a sub-frame.
Assuming that the ID of the target cell is 13 and that the initial position of
the pilot
on the first antenna port is the third subcarrier, then:
25 according to the existing technologies, and ko = N p"mod(NRB/2) ; when the
NRB
is an odd number, the ko would be a decimal number, which does not offer any
2
CA 02696171 2010-02-10
practical physical meaning; and
moreover, even if ko = N p"mod(LNRB /2 J) or ko = N p"mod(rNRB /21) , there is
still
a problem that the performance is not optimal.
y(0), ... y(15) in the physical downlink control format indicator channel are
mapped
to the following physical resources by dividing 4 continuous subcarriers in
order
except the pilots into one group:
wherein, y(0),...,y(15) stand for the data in the physical downlink control
format
indicator channel after code modulation; the NRB stands for the quantity of
the
resource blocks in the system bandwidth; and the N;p" is the proprietary ID of
each
cell.
ko = N;p"mod(NRB/2) =13mod(L25/2 J) =1 , and it is necessary to carry out a
modulus of NRB x NRB = 25 x 12 = 300 on k;
y(0).... y(3) are mapped to the resource elements in which a resource element
group k locates, and k= ko =1;
ts y(4),...y(7) are mapped to the resource elements in which the resource
element
group k locates, and k= kQ +LNRB/4] =1+L25/4] = 7;
y(8),...y(11) are mapped to the resource elements in which the resource
element
group k locates, and k=ko+L2xNRB/4]=1+12xNRe/4]=13; and
y(12).... y(15) are mapped to the resource elements in which the resource
2o element group k locates, and k = ko +L3 x NR8I41=1+L3 x 25/41=19 .
Fig. 2 is a schematic illustration of mapping a physical downlink control
format
indicator channel in a 3GPP LTE (with 5M-bandwidth) system according to
relevant
technologies. As shown in Fig. 2, the code-modulated data y(O),...,y(15) in
the
downlink control format indicator channel are mapped to the resource elements
25 numbered 6, 7, 9, 10 and 42, 43, 45, 46 as well as 78, 79, 81, 82 and 114,
115, 117,
118.
3
CA 02696171 2010-02-10
It can be seen in Fig. 2 that the range of physical elements which are mapped
to
a physical downlink control format indicator channel by the existing solution
is only
half of the bandwidth, without obtaining a maximum gain of frequency
selectivity.
In the LTE system, the resources in the physical downlink control format
indicator
channel are allocated based on 4 continuous subcarriers as a group, while in
the
system bandwidth and except the pilots, the resources are divided into groups
of 4
continuous subcarriers (the pilots are skipped over if they are encountered),
so the
total number of the groups is 2NRB (because one RB contains 12 carriers, while
one
RB also contains 4 subcarriers used for dual-antenna pilots). And there are 16
lo modulated data in the physical downlink control format indicator channel
which need
to be mapped onto 4 groups (each group has 4 subcarriers). If mapping should
be
carried out according to the formula in the above mentioned draft standard,
then the
data in the physical downlink control format indicator channel would be
distributed
unevenly over the entire system bandwidth, and thereby that is unable to
obtain the
maximum gain of frequency diversity.
SUMMARY
The present invention aims to solve the problem of uneven distribution of
PCFICH data over the entire system bandwidth caused by the mapping methods in
2o relevant technologies through providing a method for mapping a physical
downlink
control format indicator channel to physical resources.
The present invention provides a method for mapping a physical downlink
control
format indicator channel to physical resources, comprising: mapping data
y(0).... y(15)
in a physical downlink control format indicator channel to physical resources
according to the following method by combining 4 continuous subcarriers in
order
except the pilots into a group: y(0),...y(3) are mapped to the resource
elements in
which a resource element group k1= ko locates; y(4),...y(7) are mapped to the
resource elements in which a resource element group k2 = ko +LNR8/2 J locates;
y(8),...y(11) are mapped to the resource elements in which a resource element
group
4
CA 02696171 2010-02-10
k3 = ko +L2NRg/2 J= ko +LNRB J locates; y(12).... y(15) are mapped to the
resource
elements in which a resource element group k4 = ko +L3NRg/2] locates; wherein:
k0 = N;o"mod(I NR6/2 J) , and the NRB stands for the quantity of resource
blocks in the
system bandwidth, and the Np" is the proprietary ID of each cell.
The present invention also provides a method for mapping a physical downlink
control format indicator channel to physical resources, comprising: mapping
data
y(0).... y(15) in a physical downlink control format indicator channel to
physical
resources according to the following method by combining 4 continuous
subcarriers in
order except the pilots into a group: mapping y(0).... y(3) to the resource
elements in
t o which a resource element group k1= komod(2 x NRB ) locates; y(4), ... y(7)
are
mapped onto the resource elements in which a resource element group
k2 =(ko +[NRB /2])mod(2 x NRB ) locates; mapping y(8), .. . y(11) to the
resource
elements in which a resource element group k3 =(ko +LNRB ])mod(2 X NRB )
locates;
mapping y(12).... y(15) to the resource elements in which a resource element
group
k4 =(ko + L3NRB /2 J)mod(2 x NRB ) locates; wherein: ko = N p"mod(X * NRB ),
and the
NRB stands for the quantity of resource blocks in the system bandwidth, and
the N D"
is the proprietary ID of each cell, and the X is a positive integer.
Furthermore, when the X is 1, ko = N;p"mod(NRB ). At this time, mapping data
y(0).... y(15) in a physical downlink control format indicator channel to
physical
2o resources according to the following method by combining 4 continuous
subcarriers in
order except the pilots into a group: y(0).... y(3) may be mapped to the
resource
elements in which a resource element group k1= komod(2 x NRB ) locates; y(4),
... y(7)
may be mapped to the resource elements in which a resource element group
k2 =(ko + LN~B /2 J)mod(2 x NRB ) locates; y(8), ... y(11) may be mapped to
the
resource elements in which a resource element group k3 =(ko +I NRB,)mod(2X
NRB)
5
CA 02696171 2010-02-10
locates; and y(12),...y(15) may be mapped to the resource elements in which a
resource element group k4 =(ko +L3NRB/2 J)mod(2 x NRB ) locates.
Furthermore, when the X is 2, ko =N;p"mod(2xNRB). At this time, mapping data
y(0).... y(15) in a physical downlink control format indicator channel to
physical
resources according to the following method by combining 4 continuous
subcarriers in
order except the pilots into a group: y(0).... y(3) may be mapped to the
resource
elements in which a resource element group k1= komod(2 x NRB ) locates; y(4),
... y(7)
may be mapped to the resource elements in which a resource element group
k2 =(ko + LNRB /2 J)mod(2 x NRB ) locates; y(8), ... y(11) may be mapped to
the
to resource elements in which a resource element group k3 =(ko +[NRB ])mod(2x
NRB)
locates; and y(12),...y(15) may be mapped to the resource elements in which a
resource element group k4 =(ko +L3NR6/2 J)mod(2 x NRB ) locates.
Furthermore, when the X is 2, ko = N;p"mod(2 x NRB ); at this time, mapping
data
y(0).... y(15) in a physical downlink control format indicator channel to
physical
resources according to the following method by combining 4 continuous
subcarriers in
order except the pilots into a group: y(0).... y(3) may be mapped to the
resource
elements in which a resource element group k1= N,p"mod(2 x NRB ) locates;
y(4), ... y(7) may be mapped to the resource elements in which a resource
element
group k2=(Np"+LNRB/2J)mod(2xNRB) locates; y(8),...y(11) may be mapped to the
2o resource elements in which a resource element group k3 =(N p" + LNRB
J)mod(2 x NRB )
locates; and y(12),...y(15) may be mapped to the resource elements in which a
resource element group k4 =(N;p" + L3NRB /2 J)mod(2 x NRB ) locates.
The present invention can offer the maximum gain of frequency diversity by
defining group mapping rules to achieve even distribution of the data in a
physical
downlink control format indicator channel over the entire system bandwidth.
6
CA 02696171 2010-02-10
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings described here are used to provide further understanding of the
present invention and constitute a part of the present invention, and the
illustrative
embodiments for the present invention and their explanations are used to
interpret the
present invention and do not constitute any improper restriction on the
present
invention. Among the drawings:
Fig. 1 is a schematic illustration of a resource block and a resource element
in a
3GPP LTE (with 5M-bandwidth) system based on relevant technologies;
Fig. 2 is a schematic illustration of mapping a physical downlink control
format
lo indicator channel in a 3GPP LTE (with 5M-bandwidth) system based on
relevant
technologies;
Fig. 3 is a schematic illustration of mapping a physical downlink control
format
indicator channel in a 3GPP LTE (with 5M-bandwidth) system corresponding to
Method (1) based on the embodiments of the present invention; and
Fig. 4 is a schematic illustration of mapping a physical downlink control
format
indicator channel in a 3GPP LTE (with 5M-bandwidth) system corresponding to
Method (2), Method (3) and Method (4) based on the embodiments of the present
invention.
2o DETAILED DESCRIPTION
The exemplary embodiments of the present invention are described below based
on the drawings attached; it should be understood that the exemplary
embodiments
described here are only used to describe and explain the present invention
rather than
limit the present invention.
FUNCTIONAL OVERVIEW
The main idea of the present invention is that: the 16 modulated data
y(0),y(1),...,y(15) in a downlink control signaling indicator channel in the
LTE system
are divided into 4 groups in sequential order and mapped by groups, which
allows the
downlink control format indicator channel to be mapped exactly to continuous 4
7
CA 02696171 2010-02-10
resource elements recombined by resource element groups which are divided
among
all system physical resources except the pilots according to such continuous 4
resource elements in order to offer the maximum gain of frequency selectivity.
The present invention provides a method for mapping a physical downlink
control
format indicator channel to physical resources, comprising: mapping the data
y(0).... y(15) in a downlink control format indicator channel to physical
resources
according to the following method by combining 4 continuous subcarriers in
order
except the pilots into a group:
Method (1)
to Mapping the data y(0).... y(15) in a physical downlink control format
indicator
channel to physical resources according to the following method by combining 4
continuous subcarriers in order except the pilots into a group:
y(0), ... y(3) are mapped to the resource elements in which a resource element
group k1= ko locates;
y(4), ... y(7) are mapped to the resource elements in which a resource element
group k2 = ko + LNRB /2] locates;
y(8),...y(11) are mapped to the resource elements in which a resource element
group k3 = ko +L2NRB/2 J locates;
y(12).... y(15) are mapped to the resource elements in which a resource
element
group k4 = ko +[3NR6/2 ] locates; and
wherein, ko = N p"mod(LNRB /2~) , and the NRB stands for the quantity of
resource
blocks in the system bandwidth, and the N,p" is the proprietary ID of each
cell.
As shown in Fig. 3, after the above mentioned mapping processing, the
code-modulated data y(0),...,y(15) in a physical downlink control format
indicator
channel are mapped to the resource elements numbered 6, 7, 9, 10 and 78, 79,
81, 82
as well as 156, 157, 159, 160 and 228, 229, 231, 232. The initial position of
the
physical resources in the physical downlink control format indicator channel
lies at the
8
CA 02696171 2010-02-10
first quarter position of the available bandwidth.
Method (2)
Mapping the data y(0).... y(15) in a physical downlink control format
indicator
channel to physical resources according to the following method by combining 4
continuous subcarriers in order except the pilots into a group:
y(0).... y(3) are mapped to the resource elements in which a resource element
group k1= komod(2 x NRB ) locates;
y(4),...y(7) are mapped to the resource elements in which a resource element
group k2 =(ko + LNRB /2 J)mod(2 x NRB ) locates;
to y(8),...y(11) are mapped to the resource elements in which a resource
element
group k3=(ko+LNRB J)mod(2xNR6) locates;
y(12),...y(15) are mapped to the resource elements in which a resource element
group k4 =(ko + L3NRB /2])mod(2 x NRB ) locates; and
wherein, ko =N;p"mod(NRB), the NRB stands for the quantity of resource blocks
in the system bandwidth, and N;p" is the proprietary ID of each cell.
As shown in Fig. 4, after the above mentioned mapping processing, the
code-modulated data y(0),...,y(15) in a physical downlink control format
indicator
channel are mapped to the resource elements numbered 78, 79, 81, 82 and 150,
151,
153, 154 as well as 228, 229, 231, 232 and 0, 1, 3, 4. The initial position of
the
physical resources in the physical downlink control format indicator channel
lies at the
first one-half position of the available bandwidth.
Method (3)
Mapping the data y(0),...y(15) in a physical downlink control format indicator
channel to physical resources according to the following method by combining 4
continuous subcarriers in order except the pilots into a group:
y(0),...y(3) are mapped to the resource elements in which a resource element
group k1= komod(2 x NRB ) locates;
9
CA 02696171 2010-02-10
y(4),...y(7) are mapped to the resource elements in which a resource element
group k2 =(ko + LNRB /2 J)mod(2 x NRB ) locates;
y(8),...y(11) are mapped to the resource elements in which a resource element
group k3 =(ko +[NRB ])mod(2 x NRB ) locates;
y(12).... y(15) are mapped to the resource elements in which a resource
element
group k4=(ko+[3NRB/2])mod(2xNRg) locates; and
wherein, ko = N;p"mod(2 x NRB ), and the NRB stands for the quantity of
resource
blocks in the system bandwidth, and the N p" is the proprietary ID of each
cell.
As shown in Fig. 4, after the above mentioned mapping processing, the
io code-modulated data y(0),...,y(15) in a physical downlink control format
indicator
channel are mapped to the resource elements numbered 78, 79, 81, 82 and 150,
151,
153, 154 as well as 228, 229, 231, 232 and 0, 1, 3, 4. The initial position of
the
physical resources in the physical downlink control format indicator channel
may lie at
any position of the available bandwidth.
Method (4)
Mapping data y(0),...y(15) in a physical downlink control format indicator
channel
to physical resources according to the following method by combining 4
continuous
subcarriers in order except the pilots into a group:
y(0),...y(3) are mapped to the resource elements in which a resource element
group k1= N;p"mod(2 x NRB ) locates;
y(4),...y(7) are mapped to the resource elements in which a resource element
group k2=(N,o"+I NRB/2J)mod(2xNRB) locates;
y(8),...y(11) are mapped to the resource elements in which a resource element
group k3=(Np"+LNRB J)mod(2xNRB) locates;
y(12),...y(15) are mapped to the resource elements in which a resource element
group k4 =(N;p" + L3NRB /2 J)mod(2 x NRg ) locates; and
CA 02696171 2010-02-10
wherein, the NRB stands for the quantity of resource blocks in the system
bandwidth, and the N;p" is the proprietary ID of each cell.
As shown in Fig. 4, after the above mentioned mapping processing, the
code-modulated data y(0),..., y(15) in a physical downlink control format
indicator
channel are mapped to the resource elements numbered 78, 79, 81, 82 and 150,
151,
153, 154 as well as 228, 229, 231, 232 and 0, 1, 3, 4. The initial position of
the
physical resources in the physical downlink control format indicator channel
may lie at
any position of the available bandwidth.
For above mentioned Method (3) and Method (4), the initial position of the
io physical resources in the physical downlink control format indicator
channel may lie at
any position of the available bandwidth. More initial positions mean that
there are
more mapping patterns of the physical downlink control format indicator
channel.
The more patterns there are, the better randomization degree of mutual
interferences
among the physical downlink control format indicator channels in neighboring
cells will
be obtained. For Method (3) and Method (4), only the forms of expression are
different, but their mapping positions are the same.
The present invention can offer the maximum gain of frequency domain
selectivity by defining group mapping rules to achieve even distribution of
data in a
physical downlink control format indicator channel over the entire system
bandwidth;
moreover, no error would arise even when the quantity of available resource
blocks is
an odd number.
Obviously, those skilled in the art should understand that the individual
modules
or individual steps in the present invention as mentioned above can be
realized by
using a general-purpose computing device, that they can be either integrated
in a
single computing device or distributed over a network comprised of multiple
computing devices and that, optionally, they can be realized by using program
codes
executable by such a computing device so that they can be stored inside a
storage
device and executed by a computing device, or they can be individually made
into
individual integrated circuit modules, or they can be realized by making the
multiple
11
CA 02696171 2010-02-10
modules or steps in them into individual integrated circuit modules. In this
way, the
present invention is not restricted to any specific combination of hardware
and
software.
The above mentioned are the exemplary embodiments of the present invention
only and are in no way intended to limit the present invention. For those
skilled in the
art, various modifications and changes may be made to the present invention.
Any
modification, equivalent substitute and improvement within the spirit of the
present
invention are deemed to be included within the scope of protection of the
present
invention.
12
